In the treatment of patients with certain kinds of cancer or rheumatoid arthritis, methods are known in which radioactive particles are introduced intravascularly to a tumor site (radioembolism) or locally into the synovial fluid in a joint in order to trap the radioactive particle at a particular site for its radiation effect. Similar methods are used for imaging parts of the body, organs, tumors, and so forth.
According to this technique, a quantity of the radioactive particles are injected into a localized area of the patient to be imaged and/or treated. For imaging, gamma emitting materials are commonly used to label carriers that provide imaging of a tissue area, tumor or organ. Some of these carriers have a specific affinity for certain binding sites or biochemical targets allowing target specific or location specific uptake of the labelled carrier.
Radiological imaging of various tissues in the human body is commonly accomplished using Technetium-99m. 99m-TC is a well-known radioactive isotope used for radiodiagnostics. It emits detectable low level 140 keV gamma rays, has a half-life of 6 hours and decays to Tc-99 in 24 hours (93.7%). It is used for imaging and function studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, bone, blood, and tumors. It is reported to be used in over 20 million diagnostic nuclear medicine procedures each year.
Targeted radiation therapy using microparticles or microspheres is also a well-developed field radioisotope therapy. Radionuclides such as Yttrium-90 and Holmium-166 are commonly used radioactive beta emitters in microsphere radiotherapy. Polymer microspheres such as albumin, poly-lactic acid derivatives, and so forth, and glass microspheres, are both generally known in the medical arts for use in delivering both pharmaceuticals and radiopharmaceuticals to specific tissue sites.
However, a need remains for a radioactive microparticle for delivery of one or more radiopharmaceuticals and which have characteristics which will permit the microparticles to be suitable for injection into a patient for localized imaging or therapy.